This research analyzes changes in individuals' social orientations during periods of transition across the lifespan. It is suggested that changes in knowledge during the course of a transition influence how an individual approaches and responds to relevant social information. Because the focus is on transitions relevant to social, rather than cognitive outcomes, they are referred to here as "socializing transitions." A common conceptualization is applied to three major instigators of socializing transitions: changes in social understanding (about gender and stable, personal traits), social experiences (the first few years of school and hospitalization), and biologically based role changes (becoming a parent for the first time). The changes in social orientations predicted during these transitions are conceptualized in terms of three explanatory constructs: motivation to acquire information; information processing; and the meaning or significance of the information. It is hypothesized that individuals are maximally motivated to acquire certain kinds of information during early stages of a transition but that once conclusions are drawn, changes in motivation and information processing make them difficult to modify. Such changes are important because of the implication that the information available during relatively circumscribed periods of a transition control significant socialization outcomes of that experience. Six sets of studies are proposed, involving both cross-sectional and longitudinal designs, and combining self-reports, observational techniques, and experimental manipulation. The theoretical significance of the research involves an increased understanding of intervening processes contributing to transformations in personal and interpersonal perceptions and behaviors often resulting from a period of transition. These processes are expected to have general applicability to any transition. Moreover, because the research involves natural settings, the findings have practical, mental health applications for these settings. Study Set 5, for example, examines children's adaptation to a brief stay in a hospital. The present focus on developmental change in information-seeking and level of understanding will be useful for developing programs to meet the needs of children at different ages, and thereby minimize the negative psychological consequences of hospitalization. Similar though less direct implications are foreseen with respect to the proposed research on performance-related self esteem in school, and affective disorders after the birth of a first child.